The invention relates to lens barrel extending and retracting mechanisms, and in particular to slim-sized lens barrel extending and retracting mechanisms with a zoom lens having a housed position and a photographic position.
The size of cameras is increasingly required to be more slim and thin. A thin and compact camera particularly in size is demand for those traveling light. Thus, in order to provide a slimmer design, the size of lens barrel units must be reduced. The size of most conventional cameras is reduced by decreasing the gap between the lens group and photographing device when the camera is not in use by housing the lens barrel in the body thereof.
Japan patent No. 2003-315861 discloses a collapsible lens barrel and method for collapsing a lens barrel. A part of a lens group in the housed position is retracted from a photographing optical axis. A second lens group is retracted from the object side and housed in a camera body.
Japan patent No. 2004-85934 discloses an extending cam mechanism for a zoom lens barrel, which not only limits the extent of movement of lenses and movement precision but also makes a cam ring small-sized.
Although the size of the lens barrel is reduced, the optical performance should be maintained as well. In a conventional zoom digital camera, an optical photography system typically comprises three lens groups. Zooming and retracting are performed by moving each lens group in the direction of the photographic optical axis. Deviation of the photographic optical axes of the lens groups, particularly deviation of the photographic optical axes of the first lens group and the second lens group from the object side, and relative tilt of the photographic optical axes of the first lens group and the second lens group may greatly affect optical performance of the camera. In both Japan patent No. 2003-315861 and No. 2004-85934, since only the second lens group is retracted via individual retracting mechanism, the lens groups may be tilted and eccentric in parallel such that optical performance is difficult to maintain.